In a classroom at Adelphi University in Garden City, 13-year-old Chris Stratakis is creating "petrified boots" for his Minecraft video-game character, boots that will let his character jump from higher locations without being injured.

He'll add them to his arsenal, which includes, among other things, a jet pack for flying.

Chris is at a brand-new Minecraft camp that California-based iD Tech Camps added to its technology offerings this year in response to the phenomenal popularity of the game that has sold more than 11 million copies since 2009, many of them to tweens and teens.

"Minecraft is a good way to expand your imagination," says Chris, of Manhasset, who is learning Java programming at camp to allow him to enhance his play by creating modifications. "It's like 3-D Legos."

Parents may be confused by the game. "I wish they knew how much fun it is," camper Jack Dauber, 13, of Oceanside says. To help Mom and Dad, we've compiled this quick guide to Minecraft:

Minecraft is like the continuation of Lego play, but kids are using the blocks to build their own 3-D worlds on computers. They construct buildings, amusement parks with roller coasters, whatever they imagine.

They expand into different "biomes" -- environments such as a forest or a desert. The blocky characters also look like they are made of Legos.

The two basic modes of play are "survival" and "creative." In survival, a player must "mine" materials such as wood before he or she can "craft" buildings, furniture, tools and more -- hence the name Minecraft.

While building, players must protect themselves from zombies. But there's no blood, no gore; this is not a first-person shooter game like "Call of Duty." When you kill a zombie, it just crumbles and disappears. If your character "dies," you "respawn" in your bed.

Creative mode gives players unlimited building materials for essentially a construction enterprise. "Kids just love being able to finish making it and stand back and go, 'That's so epic,' " says Christopher Rudder, curriculum developer for iD Tech Camps.

What is the goal?

"The coolest part about Minecraft is that there's no ultimate goal," Rudder says. It's not like a game such as Super Mario Bros., in which characters have a premade scenario and have to accomplish set tasks.

Surfing the web is a good way to get more familiar with the game. Visit bit.ly/12lW3EQ guide to start, or Google "Top 5 Minecraft time lapse" to see fast-forward versions of worlds created from scratch. Scores of people have taped themselves playing; some of those YouTube videos have had millions of views.

Where to buy?

Purchase Minecraft for $26.95 at minecraft.net, or an Xbox version for about $20. There's also an app called Minecraft Pocket Edition for $7. Minecraft was created by Swedish programmer Markus "Notch" Persson and is now run by a company called Mojang.

Check your local library for offerings, and register quickly. Huntington Library has a program Aug. 7 during which library cardholders can show off their Minecraft creations by bringing a flash drive of their work to be projected on a big screen.

Hauppauge Library offers Minecraft 101 on Aug. 18 to teach the basics of mining resources, building tools and crafting to grades 1 to 5. Both programs are full and have waiting lists.